Extraterrestrials have been visiting our planet for decades. Whether it’s “Twilight Zone” aliens inviting us onto their ship for a meal or big black monoliths helping ape-men evolve in “2001,” visitors from beyond the stars have always struck humankind with an uneasy cocktail of rapturous wonder and absolute dread. What most of these science-fiction tales can agree on is that aliens may be scary, but nice aliens are even scarier.

“Childhood’s End” is in this vein: A three-night miniseries based off the 1953 novel of the same name by Arthur C. Clarke, the original book is a seminal work in science-fiction and has left a highly visible mark on the genre. Which may be why the story is, at first, familiar. Titanic alien spacecraft appear over Earth’s major cities, drawn to national capitals like moths to a flame. The aliens, dubbed “Overlords,” quickly eliminate all war and conflict, creating a considerable gap in humankind’s collective schedule. This allows us to end world hunger, climate change, disease and any other malaise society could potentially experience.

In adapting the original work for 2015, Clarke’s Cold War anxieties and underlying 1950s racism are wisely and delicately removed and the story is updated with more contemporary references; some (Israel/Palestine, oil crises in the Middle East, North Korea) feel a little forced at times, but in general, the transition from the middle of the 20th century to the early years of the 21st feels lucid and natural. In addition, the Overlord’s chosen mouthpiece, Ricky Stormgren, is changed from the U.N. Secretary General to a square-jawed, Middle America everyman. This and other similar alterations allow for some character exploration and melodrama that provides a personal touch oft-absent in science-fiction and in the Clarke novel. This isn’t to say that the original isn’t dutifully represented. The adaptation is faithful before it reimagines and reboots. Because of this, and due in part to the legacy of its source material, the setup and execution of “Childhood’s End” feel comfortably familiar in terms of the science-fiction genre.

Where “Childhood’s End” succeeds is that it balances its convention and its twists in fairly equal measure. Black-suited government caricatures oppose the Overlords’ arrival and try to cover it up. The extraterrestrial supervisors use technology that looks like the product of a merger between Tesla Motors and Apple Computers. Once utopia is achieved, every earthling suddenly decides to exclusively wear beige. These tropes never feel heavy-handed or parodic, yet “Childhood’s End” remains aware of them and never takes itself too seriously.

These conventions only add to the intrigue of “Childhood’s” eventual twists and turns. While utopia, at first, seems to be the idyll humanity has always hoped for, a chain reaction of bizarre events upset our expectations. We start to question where these sci-fi standards we so readily accepted are coming from. Are the Overlords and their power the product of science, or magic? Accident, or intent? Punishment, or reward?

While “Childhood’s End” does an excellent job of raising these deep, philosophical questions, it hesitates to really dive into them. The residents of the new world order reflect on utopia, but only ever glaze over its implications. One couple may be debating love and loss, but before we have a chance to think, we move on to a discussion of religion, then quickly to a question regarding scientific inquiry. This brevity is not always appreciated. Each of the humans in “Childhood’s End” is pushed in the direction of some hard sought truth of the universe, but never pushed hard enough to fall into the meat of things.

What sci-fi as a genre does best is ask the big questions and point us toward a solution in broad, hypothetical-metaphorical terms. Creation, death and religion are concepts we may never fully understand, but through an imagined alien gift, Clarke and other authors give us the pretext to think long and hard about our existence. The impressive ensemble of “Childhood’s End” attempt this, but don’t always go far enough to succeed. Juggling this many characters, stories and ideas while remaining true to the source material is a difficult task, but it would have been nice to linger on some of the more mind-bending concepts lying beneath the surface.

That being said, “Childhood’s End” is incredibly entertaining. Fans of sci-fi can get quickly lost in the mysterious new utopia, and the less inclined viewer will still be engaged by the mystery of the Overlords. The special effects are impressive and well designed. The acting is tight and engaging, only straying into “War of the Worlds” hysteria when appropriate and needed. The direction is solid, shot like the best of sci-fi blockbusters. The miniseries format feels like a natural fit for the novel, with each episode ending and beginning on a satisfying yet cliffhanging note. Overall, the parts create a high-quality whole that is undeniably enjoyable.

Ultimately, “Childhood’s End” is a successful adaptation of a much-beloved novel that will satisfy fans and newcomers alike — wrapped nicely at both ends with colorful characters and effects, but faintly lacking a little something in the middle. The result is an enjoyable, interesting miniseries that is certain to entertain, but bound to keep you guessing.